Many products, including consumer and professional products, can be used more effectively by an end user if they include a feature that informs a particular condition or state of use for the products. For instance, in the area of consumer absorbent products, especially in the diaper, feminine hygiene, or paper tissue markets, manufacturers have recently investigated various ways of providing a wetness sensitive indicator that can give a signal to the consumers or end-users and allows them to change or replace the absorbent products in a timely manner. These color based indicators can provide more satisfaction and enhance the consumer's experience of the products by relaying real time informing about wetness conditions without any additional equipments, such as electronic devices. Such wetness sensing technology can improve levels of hygiene and care, especially for persons who cannot easily communicate to caregivers such as newborn babies or incapacitated patients. For instance, the signal can prevent a baby's or patient's skin from over exposure to moisture which may cause a number of problems such as rashes.
Many kinds of wetness indicating technologies have been described in the literature for consumer products, but none of the currently existing approaches is ideal. An example of a visual wetness indicator is a color indicator. Color indicators can either indicate a change in condition or a degree of use through a change from “no color” to “color” (or vice versa) or through a change from one color to a different color.
Exemplary conditions that could be monitored using a color indicator include physical conditions such as the presence of moisture and chemical conditions such as a change in pH. Exemplary consumer products that could be more effective and deliver more benefits to end users by incorporating a suitable color indicator include absorbent articles, facial tissues, bath tissue, paper towels, household cleaning items and personal cleaning wipes. Exemplary professional products that could be more effective and deliver more benefits to end users by incorporating a suitable color indicator include products for medical use, safety garments, industrial cleaning products and nonwoven materials.
For instance, certain adhesive-based wetness indicators give very poor color contrast, and the indicator colors also can suffer from dye leaching off of its substrate. Other water-dissolved-dye-based wetness indicators suffer from low sensitivity and again low color contrast. Given these shortcomings, workers in the colorant indicator area would welcome a new technical approach to generate durable and highly visually-contrasting colorants. Color indicators are well known and are available in various forms. Desirable performance attributes include durability and good retention (i.e. the color indicator remains where intended and does not bleed or leach out into other components of the product within which it is being used). Depending on the product application, it may also be desirable to have the structure in which the color indicator is used be wettable, but water insoluble. For purposes of applying the color indicator to a component of a product, it may also be desirable to have a color indicator that can be applied in liquid form at room temperature. When the color indicator is in a liquid form at room temperature, the color indicator can be printed (just like an ink composition) onto the desired component of a product. The ink form can make easier demonstration to provide more attractive graphic by being adjusted into current printing methods, such as ink jet, flexographic or gravure methods.
Examples of how color indicators are already incorporated into consumer products include diapers that have wetness sensors. Some of the wetness sensors used in diapers change color to indicate wetness while others lose color in response to wetness (i.e. the color fades or disappears when it is dissolved by water). The concept of incorporating a color-changing composition into a wearable article (such as a disposable diaper) is known in the art. For example, U.S. Pat. No. 7,159,532 issued to Klofta et al. (hereinafter “the '532 patent”) is directed to wetness indicating compositions having improved colorant retention and durability for use with wearable articles. The wetness indicating compositions of the '532 patent have a first binding agent and a second binding agent. The first binding agent immobilizes a colorant when the colorant is in its initial color state and the second binding agent immobilizes the colorant when the colorant is in its final color state. The component materials used in the examples provided in the '532 patent are solid at room temperature as indicated by the description that they need to be melted in order to combine them. While the wetness indicating compositions of the '532 patent are capable of changing color in response to a stimulus, they are not capable of being applied to an article in liquid form at room temperature.
While the color-changing compositions known in the art provide certain benefits, there remains a need for a film-forming composition that can be applied to a substrate. There also remains a need for a composition that is durable, has good retention and that shows rapid and dramatic color change when the composition is used in a product. When the purpose of the composition is to detect the presence of wetness, there remains a need for a composition that is water-resistant and water-insoluble. Further, there remains a need for a composition that can be applied, such as by printing, at room temperature so that the composition can be applied to a substrate without heating.